1. Field of the Invention
The present invention relates to a method and apparatus for reducing power consumption of an ethernet transceiver. More specifically, the present invention conserves power of a notebook computer by using an auto-negotiating ethernet transceiver which can detect when an ethernet link has been physically disconnected. The present invention then causes the ethernet transceiver to enter into a low power mode to reduce energy consumption until the physical connection of a network cable is reconnected.
2. The State of the Art
Ethernet transceivers are becoming more ubiquitous in portable computers as connections to local area networks (LANs), wide area networks (WANs), other Intranet configurations, and to the Internet are becoming necessary elements of doing business in an information age. The advantages of sharing information and resources by use of networks are realized by many computer users. It is also the case that many computer users prefer the mobility provided by portable computers also known as laptop, notebook and sub-notebook computers. However, it is only as use of portable computers has become more widespread that some of the problems inherent to the use of an ethernet (a type of computer network) transceiver with a portable computer has been recognized.
In particular, one problem that has manifest itself becomes an issue when a portable computer which is connected to a network is physically disconnected without terminating the network session. In other words, the problem arises when a connection to a network is severed by physically removing a network connector such as an RJ-45, AUI, or BNC connector from an ethernet transceiver in the portable computer without first logging off the network. This situation typically arises when the computer user needs to move the portable computer to a new location, such as to a different office, and does not take the time to log off of the computer network.
This situation occurs even when the computer users is aware of being connected to the computer network. However, the computer user is also probably aware that there is typically no danger to the portable computer by physically disconnecting a running computer from the network. Furthermore, as long as no file transfer is taking place between the portable computer and the network, there is no danger to the user's files on the network. Accordingly, there is no reason, which would be apparent to the computer user, why the network connection should not be removed so that the portable computer can be made portable for use elsewhere.
Nevertheless, there are consequences of moving the portable computer without terminating the network connection. To understand these consequences, it is necessary to realize facts which are also typical to the scenario described above. First, if the computer user is going to disconnect the network connection and move the portable computer, it is also likely that a power cord to the portable computer is going to be disconnected. Second, this means that the portable computer will continue to operate on internal battery power until the portable computer is either shut down (turned off), or reconnected to the power cord.
It is typically of primary concern to the computer user of a portable computer that the portable computer be able to continue operation on internal battery power as long as possible. This is because the portable computer is likely to be operating off internal battery power for an extended period of time. If this is the case, the computer user is now unaware that the internal battery power is being drained at a much faster rate than can be accounted for simply by operation of the portable computer. This is because, unknown to the computer user, the network transceiver which was physically disconnected from a network cable is disadvantageously continuing to operate in a high power consumption mode.
The principles of operation of an auto-negotiating ethernet transceiver which are of concern to the present invention will now be explained. The auto-negotiating aspect of the ethernet transceiver refers to an ability to "negotiate" a connection to a host computer which is responsible for network functions. This is accomplished by first detecting ethernet activity on network cabling. This is also referred to as detecting a link. When the link is detected, the ethernet transceiver then negotiates communication parameters with the host computer so that communication can take place. These communication parameters include determining the highest performance common operating mode at which the transceiver and the host computer can operate. For example, the transceiver can determine at what speed it can communicate with other network nodes.
When the computer user physically disconnects a network cable from the ethernet transceiver, the ethernet transceiver continues to check for an ethernet link. When none is detected, the ethernet transceiver continues to check for the link approximately every two seconds. Checking for an ethernet link is an operation that is a high power draw. Accordingly, the internal battery is drained much faster than if the transceiver were not continuing to check for the link.
Therefore, it would be advantageous over the prior art to provide a method and apparatus for lowering the power drain on the internal battery of a portable computer whenever a link to a network is physically disconnected from an auto-negotiating transceiver. It would also be advantageous if the network transceiver could continue to auto-negotiate a connection to the network so that if the physical connection is reestablished, the portable computer could continue to communicate with the network.